Bonding using epoxy resin composition and nonactivated blowing agent

ABSTRACT

Epoxy resin composition consisting essentially of an epoxy resin component, curing agent, thermally decomposable blowing agent and optionally thermoplastic polymer, said composition, after curing, being capable of being broken up by expanding with the application of heat. It is used, for example, in joining cables by connecting core wires, slipping sleeve over portion where core wires have been connected, sealing said sleeve and sheath by said epoxy composition and thereafter curing said epoxy composition to form sealed portion, said sealed portion being capable of subsequent dismantlement.

United States Patent Inventors Kiyoshi Hoshii Ichlkawa-shi; Hisaolshikawa, Tokyo; Keishi Tado,

Ichikawa-shi, all of Japan App]. No. 708,317

Filed Feb. 26, 1968 Patented Oct. 26, 1971 Assignee The Fujikura CableWorks Limited Tokyo, Japan Priorities Feb. 28, 1967, June 3, 1967 Japan42/12255, 42/35160 BONDING USING EPOXY RESIN COMPOSITION AND NONACTIVATED BLOWING AGENT 15 Claims, 1 Drawing Fig.

f 5 6 References Cited UNITED STATES PATENTS 2,956,037 10/1960 Venable260/306 3,127,291 5/1964 Betz etal. 156/49 3,348,640 10/1967 Thompson eta1. 188/250 3,406,131 10/1968 Kuhlkamp et al.... 260/25 9 3,429,8382/1969 Hersh 260/2.5

3,454,506 7/1969 Brack..... 260/25 3,471,350 10/1969 OBerry et al.156/184 FOREIGN PATENTS 1,081,350 8/1967 Great Britain 156/49 PrimaryExaminer-Carl D. Quarforth Assistant Examiner-E. A. MillerAttorney-Wenderoth, Lind & Ponack sealing said sleeve and sheath by saidepoxy composition and thereafter curing said epoxy composition to formsealed portion, said sealed portion being capable of subsequentdismantlem'ent.

PATENTEDUBT 28 I9?! 3, 6 l5 96 O kwosul HOSHII. HLSAO ISHIKAWA Al-lbKEISHI TAUO.

INVENTORS BYUSMJM$ LIZLPMLL ATTORNEYS material in contact therewith whencuring without giving off any volatile substances in so doing, andfurthennore because of their excellent mechanical strength andelectrical insulating property. Thus, the known epoxy resin compositionsare which contain a curing agent but, on the other hand, the cured resincomposition expands readily by heating to result in numerous cracksbeing formed therein, with the consequence that it becomes possible toeasily remove the cured resin composition from its place of applicationwith relatively small effort.

As the epoxy resin component to be used in the invention, any compoundor high molecular compound having two or more epoxy groups in itsmolecule can be used. However, it is preferred that as this epoxy resincomponent use is made of principally the condensation product ofepichlorohydrin and a polyhydric phenol and/or a polyhydric alcohol and,in particular, a bis-epoxy compound of the formula satisfactory for suchpurpose as the permanent adhesion structures or aggregates. However,with respect to such uses as the temporary stopping of spaces ofstructures or the temporary stopping of spaces of structures or thetemporary adhesion of aggregates they were not entirely satisfactory.

For example, the conventional epoxy resins are used as.

putty for securing window glass to sashes on account of their superioradhesion and sealing effects when used with structures. However, when aonce packed putty is to be removed for replacing the windowpane,difficulty is frequently encountered in removing the putty because theadhesiveness and mechanical strength of the epoxy resins are too great.

On the other hand, while the known putty materials other than the epoxyresins can be removed relatively easily after having been used forstopping the spaces of structures, they had the drawback that theiradhesiveness to the structure and sealing effect were very poor.

Again, in sealing electric cables or wires such as power andcommunications cables, a method is quite prevalent whichcomprises firstjoining the core wires, slipping a sleeve over the core wire joint andthen sealing the sleeve and the sheath of the electric wires or cables.Lately, a proposal is being made of using the epoxy resins as thesealing agent in this case. However, when the need arises of dismantlingthe sealed portion for the purpose of providing a new branch in a oncejoined electric wire or cable or of inspecting the cable there is thedrawback that the breaking up and removal of the once packed and curedepoxy resin is very difficult due to its great toughness.

It is therefore an object of the invention to provide a new epoxy resincomposition which can achieve a tight seal by its strong adhesion to thesurface of the material in contact therewith when packed in the spacesof structures or applied to the surroundings of the boundaries ofaggregates but, on the other, can be readily broken up and removed bymeans of heat after its application.

Another object of the invention is to provide a new epoxy resincomposition which is capable of being cured while latently possessingthe property of being expanded by heating and, in addition, does notsuffer by comparison with the conventional epoxy resin compositions withrespect to adhesiveness, mechanical properties and electrical insulatingproperty and yet possesses the hereinbefore noted property.

Other objects and advantages of the invention will become apparent from.the following description. It was found that these objects could beachieved by an epoxy resin composition which is curable while latentlypossessing the property of being expandable by heating, and specificallyby an epoxy resin composition comprising an epoxy resin component, acuring agent and a thermally decomposable blowing agent, as itsrequisite constituents.

Namely, since the epoxy resin composition of this invention comprises anepoxy resin component and a curing agent to which has been furtherincorporated a thermally decomposable blowing agent, it can be cured atambient temperature as in the case with the conventional epoxy resincompositions of wherein R is a bivalent hydrocarbon group,

preferably a residue resulting after removing two hydroxyl groups frompolyvalent phenols or aromatic polyhydric alcohols, and n is a numberfrom 0 to 8 and preferably from 0 to 2. The bisphenol such as2,2-bis(4'-oxyphenyl) propane or the bisepoxy compounds obtained fromepichlorohydrin and such polyhydric alcohols as resol are particularlysuitable for use as the epoxy resin component of this invention in viewof their ready availability.

While the bis-epoxy compounds of the foregoing general formula exhibitvaried properties ranging from those which are liquids of low viscosityto high viscosity or are of a pasty form depending upon the class of thebivalent group R and the value n all forms can be used in the invention.The term epoxy resin component as herein used, is meant to include allof the these epoxy compounds.

On the other hand, the curing agent which can be used in the inventionincludes those difunctional compounds which are capable of readilyreacting with the epoxy and/or hydroxyl group. These curing agents arethose low molecular or high molecular compounds which are known per se.Usable, for example, are diamines or polyamines having active hydrogen,dimercaptans, carboxylic acid amides, polyamides, polysulfides orsulfonic acid amides, or the mixtures of these compounds. Further,usable are the commercially available curing agents having thesecompounds as their principal ingredient.

It is preferred that the curing agent to be used in the invention is onewhich can cure the epoxy resin component in a relatively short period oftime at a temperature lower than the decomposition temperature of thehereinafter described blowing agent, and particularly at ambienttemperature. For this reason the use of diamines, polyamines or therelatively low molecular weight polyamide resins or polysulfides isespecially recommended. Needless to say, the foregoing curing agents canbe used in combination in accordance with the known prescriptions. Forexample, the curing speed of the epoxy resin component can be controlledby using a low molecular weight amine and a high molecular weightpolyamide in combination.

The ratio in which the epoxy resin component and the curing agent aremixed may be that usually used heretofore in curing the epoxy resins.While the proportion in which the two components are mixed will varyconsiderably depending, for example, on the class of the two componentsto be used, generally speaking, a proportion in which the curing agentis contained in the amount of 5 to parts by weight per 100 parts byweight of the epoxy resin component is to be preferred from thestandpoint of the curing operation but, on the other hand, a proportionin which the curing agent ranges from 30 to 60 parts by weight per l00parts by weight of the epoxy resin component is to be desired from thestandpoint of the blending operation.

The blowing agent used in the invention is of the type which does notdecomposes during the curing of the epoxy resin component but remains inthe resin composition to decompose upon being heated and evolve a gas.

As such a blowing agent, usable are the well-known solid blowing agentswhich are used in the production of the foamed structures of rubber orthe vinyl chloride resins. For example, usably are such organic blowingagents as azoisobutyronitrile, dinitrosopentamethylenetetramine,azodicarbamic acid amide, benzenesulfonylhydrazide and its derivatives,p,p-oxybis (bcnzenesulfonylhydrazide) and its derivatives and N ,N-dinitroso N,Ndimethylterephthalamide.

Generally speaking, the curing of the epoxy resins is accompanied by thegeneration of heat. Hence, for ensuring that the blowing agent does notdecompose by this heat it is particularly desirable that the blowingagent chosen from among the foregoing blowing agents is one which has adecomposition temperature in the range of 90 to 200 C. However, if thecuring agent used is so chosen that the curing speed of the resincomposition is retarded or the amount used of the curing agent is insuch a small amount that sufficient cooling of the resin compositiontakes place during its curing, it also becomes possible to use a blowingagent whose decomposition temperature is relatively low.

It goes without saying that when the decomposition temperature of theblowing agent used is high it can also be used suitably combined with anacid blowing promotor such as oxalic acid or a urea type promotor.

While the amount of the blowing agent to be incorporated in the resincomposition in the invention varies considerably depending upon the kindof the blowing agent used, it is generally desirable to use to 50 partsby weight, and preferably to 25 parts by weight, of it per 100 parts byweight of the epoxy resin component. When the blowing agent is used inan amount less than 10 parts by weight per 100 parts by weight of theepoxy resin component, it is curable to obtain the desired expandingeffect when it is intended to break up the cured resin composition,whereas the use of the blowing agent in the amount exceeding 50 parts byweight not only is a disadvantage economically but there are cases inwhich the resin composition does not cure depending upon the kind of theblowing agent used.

It was also found according to the invention that by furtherincorporating a thermoplastic resin in the composition comprising anepoxy resin component, a curing agent and a thermally decomposableblowing agent, the breaking up and removal of the cured resincomposition from the place where it was applied could be made stilleasier.

Namely, in the case of a composition comprising an epoxy resincomponent, a curing agent and a thermally decomposable blowing agentthere is the tendency that the gas formed by the decomposition of theblowing agent by heating to escape somewhat from the cured resincomposition, but when a thermoplastic resin is incorporated this escapeof the gas resulting from decomposition of the cured resin compositioncan be prevented. In addition, the cured epoxy resin can be impartedstill more completely the latent property by which it is capable ofexpanding or forming cracks by means of heat, with the consequence thatthe breaking up of the cured resin composition becomes still more easy.

In view of the hereinabove described actions, the thermoplastic polymerwhich can be used is preferably one having a softening temperature which.either coincides with or is lower than the decomposition temperature ofthe thermally decomposable blowing agent. Hence, the thermoplasticpolymers which can be used in the invention are those chosen from thepolymers or copolymers of the alpha, beta unsaturated compounds, such aspolystyrene, methyl polyacrylate, polymethyl methacrylate, polyvinylacetate, polyethylene, polypropylene, ethylene-vinyl acetate copolymer,vinyl acetate-vinyl chloride copolymer, ethylene-ethyl acrylatecopolymer, ethylene-propylene rubber, butyl rubber and natural rubber.Of these high molecular compounds, those polymers and copolymers whosemelting point is relatively low are suitably for use as thethermoplastic polymer in the invention.

The thermoplastic polymer can be incorporated in the epoxy resincomposition as a coarse or fine powder, or in a fibrous state, or as aliquid. The amount of the thermoplastic polymer incorporated in thiscase is preferably in a range of 3 to 30 parts by weight per parts byweight of the epoxy resin component. When the thermoplastic polymer isincorporated in the amount in excess of 30 parts by weight, there is atendency to a decline in the adhesiveness as well as the sealing effectof the epoxy resin composition. On the other hand, when the amount usedof said polymer is less than 3 parts by weight, the effect of theincorporation of the thermoplastic polymer is not pronounced.

In the case of the epoxy resin composition which has been thusincorporated a thermoplastic polymer, the breaking up of the cured resincomposition is made much easier. When a strong adhesiveness and sealingeffect of great mechanical strength is desired in the cured resincomposition, the previously described epoxy resin composition notincorporated with the thermoplastic resin is used.

Besides the aforesaid essential constituents, the invention epoxy resincomposition can be incorporated with such other additives as fillers,colorants and dispersing agents, if desired.

As such fillers, usable are substances such as finely divided silica,powdered or fibrous glass, light and heavy calcium carbonate, calciumcarbonate surface-treated with aliphatic acid salts, talc, calcinedclay, rock wool, asbestos, diatomaceous earth and zinc white, or such ascarbon black in those cases where the epoxy resin composition is to beused for other than insulating purposes. Since these fillers are notonly useful for imparting bulk to the resin composition but can alsoprovide the uncured resin composition with form retaining property, itis generally preferable to incorporate them in an amount of 50 to 500parts by weight per 100 parts by weight of the epoxy resin component.

Further, metallic powders of such as aluminum or metal oxides such asferric oxide (Fe O may be suitably incorporated in the invention epoxyresin composition for improving its adhesiveness to the surface ofstructures with which it contacts, as well as improving its thermaldissipation during curing or its thermal conductivity during its breakup by heating.

Before its application the invention epoxy resin composition shouldpreferably be in either a pasty, semisolid or plastic solid state inorder that it can be applied conveniently. It is generally recommendedthat the composition be such that the degree of needle penetration ofthe plastic blend is at least 20 but not greater than 200.

When the composition is one in which the degree of needle penetration isrelatively low in the foregoing range, it is preferred that in itsapplication it be heated to a temperature below that at which theblowing agent decomposes. On the other hand, when the composition is tobe applied without heating, it is preferred that the degree of needlepenetration is in the range from 40 to 120.

The invention epoxy resin composition can be prepared by blending andkneading together the several constituents before its use. However,since it is difficult for the common user to blend the numerousconstituents uniformly and in a short period at the working place, it ispreferred that, as in the case with the conventional two-liquid systemepoxy adhesive, it be prepared separately in two systems of one thatcontains the curing agent and one that contains the epoxy resincomponent and that the two systems be mixed at the to and that the twosystems be mixed at working place when it is to be used.

In preparing the two systems, it is preferred for ensuring that themixing can be carried out uniformly that the curing of each system,i.e., the needle penetration, be made of the same degree.

In accordance with .IIS K-2530-l960 the degree of needle penetration isdefined to specify the burning of a sample by a length by which aprescribed needle penetrates the sample under the prescribed conditionsof temperature, load and time. When the needle penetrates the sample by0.1 mm., the value of the degree of needle penetration is defined as l.The normal needle of a needle penetration meter is prepared by polishingone end of a round steel rod having a diameter of Epoxy resin component:

. havinga height of about 6.35 mm. and an angle of 840-940 cutting offthe end at a position where the diameter is between 0.14 mm. and 0.16mm., tempering the rod, polishing joining electric wires or cables thecore wires are first joined together, after which a sleeve is slippedover the joined portion ofthe core wires, then the sleeve and the sheathof the sealed are sealed by means of the invention epoxy resin comitsufiiciently, and fitting it .to the central axis of a brass handle 5position and thereafter the epoxy resin composition is cured at having alength of about 32 mm. of the needle penetration me- I a temperaturelower than the decomposition temperature of ter. The normal conditionsunder which the values of the the blowing agent to form the sealedportion, then when the degree of needle penetration are measured are atemperature need arises to dismantle the sealed portion, the epoxy resinf 25 (3,, load of 100 g. (the total weight f h nggdlg, h compositionseal can be easily broken up and removed by brass handle and a poise)and time of 5 seconds. 10 merelyheating the sealed portion to atemperature above that The blowing agent is preferably incorporated inthe curing at which theblowing agent decomposes and with theapplicacomposition, for prolonging the storage life of the epoxy resinlion Ofa relatively Small forcecomposition before it use, On th th h d,h they. For removing the cured epoxy resin composition which fillsmoplastic polymer is preferably incorporated in the system I 5 th spacesof structures or which envelops aggregates, this can containing theepoxy resin component, be accomplished by heating the structure oraggregate to a A suitable illustration of the recipes of the two systemsare temperature above the decctmposifion p 0f shown b l blowing agentcontained in the cured resin composition, a temperature, say, from 80 to300 C. Then the cured epoxy P Y P 8 sysmmresin softens and expands onaccount of the decomposition of Q the blowing agent to set up numerouscracks in the interior of Pmby weigh the epoxy resin composition, withthe consequence that the cured resin composition can be broken by theapplication of a Epoxy mm compomm loo slight mechanical impacting orshearing force and hence be Fm" 30.300 very easlly removed.Thermoplastic polymer 3-30 The following nonlimitative examples aregiven for further illustration of the invention.

RECIPES l--Xl Curing component-containing system. These recipesillustrate the preparation of the epoxy resin component-containingsystem used in the invention epoxy resin composition. by Intimatemixtures of plastic substances having the penetrations indicated inTable 1, below were prepared by blending cum! H00 for 10-60 minutes attemperatures ranging between room Filler 20-200 0 Thermally decomposabletemperature and 200 C, the epoxy resln components, metalllc blowing m1040 powders, fillers and thermoplastic polymers of the kinds and in theamounts indicated in Table l, below.

, TABLE I I Recipe I I II III w V VI VII vIII IX x X! Araldite Cit-248(epoxy resin produced by Ciba Co.) Araldite CY-285 (epoxy resin producedby ,Epikote 828 epoxy resin produced by Shel Chemical Co.) Eplkote 815epoxy resin produced by Shell Chemical 00.; E ilrote 832 epoxy resinproduced by Shell Chemical Co. Malta 0 powders:

Al powder. F620; powder. or:

Clba Co.)

'Ialc Finely divided silica.

Calcium carbonate 11 helr fatty acid-treated calcium carbonate.

Polystyrene powder Ethylen e-ethyl acrylate copolymer powderEthylene-vinyl acetate oopolymer powder Butyl rubber Penetration Thus,the new epoxy resin composition of the invention can resides in thesealing of electric wires or cables. Namely, if in 75 v RECIPES XII-XXIThese recipes illustrate the preparation of the curingcomponent-containing system which is to be used in combination with theepoxy resin component-containing systems of the foregoing recipes l-Xl.

intimate mixtures of plastic substances having the penetrationsindicated in Table ll, below, were prepared byblending for 10-60 minutesat room temperature thecurin'g'agents, fillers and blowing agents of thekinds in the amounts indicated polyethylene sleeve 6. The temperature ofthis resin composiin Table II, below. tion reaches as high as 63 C. dueto its autogenous heat, and

TABLE II Recipe XII XIII XIV XV XVI XVII XVIII XIX XX XXI Curing agent:

Araldite HY 965 (curing agent produced by Ciba Co.) Araldite HY 966(curing agent produced by Ciba Co.) Varsamid 140 (curing agent producedby General Mill 00.). Varsamid 125 (curing agent produced by GeneralMill 00.). Tomide 225 (cur ng agent produced by Fuji Chemical 00.).Tomlde 245 (curing agent produced by Fuji Chemical 00.).Triethylenetetramine Tetraethylenepentamine l Fm Thiocol LP-3 (curingagent produced by Thiocol Corp.)

Talc 30 2O 80 Finely divided slllca.

Calcium carbonate Higher fatty acid surface-treated calcium carbonate"Soft clay Hard clay. Rock wool Asbestos Blowing agent:

Azoisobutyronitrile p-T oluenesulfonylhydrazide. Azodicarbamic acidamide p,p-xybis(benzenesulfonylhydrazide) Penetration EXAMPLE 1 2 thecuring is apparently completed in 113 minutes. Thus the polyethylenesheath 1 of the cable and the polyethylene sleeve 6 are intimatelyjoined.

A blowtorch flame is contacted with this cured epoxy resin compositionlayer 7 and heated for about 3 minutes. The cured epoxy resin layer 7expands, and numerous cracks are observed to form therein. Since theresin layer 7 can be completely removed by inserting a metallic rod inthe cracks About equal volumes of the epoxy resin component-containingsystem of the foregoing Recipe 1 and the curing agentcontaining systemof the foregoing Recipe X]! are mixed, and this plastic mixture isapplied to an aluminum plate as a layer 80 mm. in thickness. This epoxyresin composition layer is cured by allowing it to stand at roomtemperature. The tem- Peramre of the resin composition reaches as high yand picking the resin layer, the polyethylene sleeve 6 can be its a togno h n as f as appearance is concerned the moved in the axial directionafter removal of the resin layer, c r is Completed in 130 m This Curedep y resin 35 and hence the joint portion of the core wires can bereadily exposition layer was observed to be intimately adhered to theposed. aluminum plate.

The cured epoxy resin composition layer is heated for about EXAMPLES 3minutes by bringing the flame of a blowtorch 'in contact therewith. Theepoxy resin layer is thus softened somewhat 4() and is expanded, and theformation of numerous cracks in the layer is observed. The layer ofepoxy resin can then be readily removed from the aluminum plate eitherby pounding with a hammer or scraping with a metallic rod.

The epoxy resin component-containing systems and the curingcomponent-containing systems indicated in Table lll below, wherein theconstituents making up the systems had been mixed in the weightproportions indicated in the hereinbefore given respective recipes, aremixed in about equal volumes, following which the so obtained plasticblends are applied to aluminum plates as in example 1 and then cured byEXAMPLE 2 allowing to stand at room temperature.

This example illustrates the instance where the epoxy resin T maximumteimperawrqsthat are f g the composition ofthe invention is usedinjoining communication these resm composmons and the curmg are cables.The attached drawing is a partial sectional view of the 50 Show" InTable joint portion of a cable to which the invention epoxy resincomposition has been applied. Referring to the figure in TABLE Indescribing the joining method, core wires 3 of a paper-insu- Ep xy resinuring Maximum lated Stalpeth sheath city cable of an outer diameter mm.figfi flffig 28323 1 51 tom ci iii ri tibifi having a polyethylenesheath 1 enveloping a steel sheath 2 are System System first connected,after which a 4-mm.-thick polyethylene sleeve Recipe II Recipe XIII G3 ohaving an outside diameter of 109 mm. is slipped over the 533 if; :23oint portion. A polyethylene-aluminum laminated tape 4 18 Recipe H"Recipe 58 then wrapped about the polyethylene sheath 1 so that the alu-532: Recipe 28 128 minum side is on the outside and this is fused to theRecipe VI I I 5 polyethylene sheath 1. This is followed by furtherwrapping a Recipe XX 93 k polychloroprene adhesive tape 8 about thepolyethylene Recipe X Recipe XIX 07 10 sheath 1 at intervals in theradius direction. An annular plate 5 535: g g8 of polystyrene foam isprovided between the polyethylene Reci e IV. I Recipe XVII. 53 11ssleeve 6 and the polyethylene sheath 1 so as to ensure the 16 Recipe XIRecipe XVII-m 64 119 maintenance of the airtightness of the interior.

Next, the polyethylene-aluminum laminar tape 4 and the it can be seenthat the cured layers of these epoxy resin polychloroprene adhesive tape8 are also wrapped about the compositions are intimately adhered to thealuminum plates. polyethylene sleeve 6 in the same manner as in the caseof the When these cured epoxy resin composition layers are heatedpolyethylene sheath 1. 70 for 1-5 minutes at lOO-300 C., the layers ofthe cured resin The epoxy resin component-containing system of thecompositions soften and expand and it was observed that nuforegoingRecipe V and the curing agent-containing system of merous cracks wereformed therein. When this was pounded the foregoing Recipe XVI are mixedin about equal volumes, with a hammer or a metallic rod was inserted inthe cracks and and the o obtai d l i mixture i li d as a layer 7 to ithe resin layer was picked, it was easily removed from the aluthehereinbefore described polyethylene sheath 1 and n P We claim:

1. A method ofjoining cables with a heat decomposable seal whichcomprises physically joining said cables and applying an epoxy resincomposition to the abutting portion of said cables, said compositionconsisting essentially of:

a. an epoxy resin component,

b. a curing agent for said epoxy resin component,

c. a solid, thermally decomposable blowing agent which is decomposableat a temperature higher than the curing agent of said epoxy resincomposition,

thereafter curing said epoxy resin composition at a temperature lowerthan the decomposition temperature of said blowing agent, whereby saidcured resin composition provides a more firmly joined cable.

2. A method of joining cables according to claim 1 wherein a. the cablesto be joined are sheathed,

b. the core wires of said sheathed cables are physically joined,

0. a sleeve is slipped over said physically joined portion of the corewires so that the sleeve and sheath abut,

d. the resin composition is applied to the area in which said sleeve andsheath abut whereby said sleeve and sheath are more firmly joined.

from to 8. j

4. A process according to claim 3, wherein n is 0, l or 2.

5. A process according to claim 1, wherein the epoxy resin component isa condensation product of epichlorohydrin and 6. A process according toclaim 1, wherein the curing agent is a diamine, a polyamine, a polyamideresin of relatively low molecular weight, a polysulfide, or a mixture oftwo or more such compounds.

7. A process according to claim 1, wherein 5-100 parts by weight of thecuring agent are used per 100 parts by weight of the epoxy resincomponent.

8. A process according to claim 7, wherein 30-60 parts of the curingagent are used.

9. A process according to claim 1, wherein the blowing agent is a solidblowing agent having a decomposition temperature of -200 C. N W p 10. Aprocess according to claim 1, wherein the blowing agent is selected fromthe group consisting of azoisobutyronitrile, dinitrosopentamethylenetetramine, azodicarbamic acid amide, benzenesulphonyl hydrazide,p,p-oxybis(benzenesulphonyl hydrazide), and N,N'-dinitroso-N,N'-dimethylterephthalamide.

11. A process according to claim 1, wherein 10-50 parts by weight of theblowing agent are used per parts by weight of the epoxy resin component.

12. A process according to claim 10, wherein 15-25 parts of the blowingagent are used. V 1. A process according to claim 1, wherein said epoxyresin component includes a thermoplastic polymer in admixture therewith.7'

14. A process according to claim 13, wherein the thermoplastic polymeris a homopolymer or copolymer of one or more alpha-beta-unsaturatedcompounds.

15. A process according to claim 13, which contains 3-30 parts by weightof the thermoplastic polymer per l00 parts by weight of the epoxy resincomponent.

2. A method of joining cables according to claim 1 wherein a. the cablesto be joined are sheathed, b. the core wires of said sheathed cables arephysically joined, c. a sleeve is slipped over said physically joinedportion of the core wires so that the sleeve and sheath abut, d. theresin composition is applied to the area in which said sleeve and sheathabut whereby said sleeve and sheath are more firmly joined.
 3. A processaccording to claim 1, wherein the epoxy resin component is a compound ofthe formula wherein R is a bivalent hydrocarbon group and n is a numberfrom 0 to
 8. 4. A process according to claim 3, wherein n is 0, 1 or 2.5. A process according to claim 1, wherein the epoxy resin component isa condensation product of epichlorohydrin and an aromatic polyhydricalcohol or a polyhydric phenol.
 6. A process according to claim 1,wherein the curing agent is a diamine, a polyamine, a polyamide resin ofrelatively low molecular weight, a polysulfide, or a mixture of two ormore such compounds.
 7. A process according to claim 1, wherein 5-100parts by weight of the curing agent are used per 100 parts by weight ofthe epoxy resin component.
 8. A process according to claim 7, wherein30-60 parts of the curing agent are used.
 9. A process according toclaim 1, wherein the blowing agent is a solid blowing agent having adecomposition temperature of 90*-200* C.
 10. A process according toclaim 1, wherein the blowing agent is selected from the group consistingof azoisobutyronitrile, dinitrosopentamethylene tetramine, azodicarbamicacid amide, benzenesulphonyl hydrazide, p,p'' -oxybis(benzenesulphonylhydrazide), and N,N'' -dinitroso-N,N'' -dimethylterephthalamide.
 11. Aprocess according to claim 1, wherein 10-50 parts by weight of theblowing agent are used per 100 parts by weight of the epoxy resincomponent.
 12. A process according to claim 10, wherein 15-25 parts ofthe blowing agent are used.
 13. A process according to claim 1, whereinsaid epoxy resin component includes a thermoplastic polymer in admixturetherewith.
 14. A process according to claim 13, wherein thethermoplastic polymer is a homopolymer or copolymer of one or morealpha-beta-unsaturated compounds.
 15. A process according to claim 13,which contains 3-30 parts by weight of the thermoplastic polymer per 100parts by weight of the epoxy resin component.